Respiratory Flashcards

Question

What happens to the breakdown products of RBC

Answer 1

Haemoglobin gets split into its haem and globin components – the globin is broken down into amino acids and the haem gets broken down into iron and biliverdin. the iron combines with the plasma protein transferrin, which transports the iron in the bloodstream. in the muscle, liver and spleen, iron detaches from transferrin and combines with iron-storing proteins – ferritin and haemosiderin. when iron is released from its storage site or absorbed from the gut, it combines with transferrin and gets transported to the bone marrow where it is used for rbc production. biliverdin gets converted into bilirubin, which enters the circulation and is transported to the liver where it is secreted into the bile.

Answer 2

oxygen is relatively insoluble in water and therefore only approximately 1.5% of total oxygen is carried dissolved in the plasma. the remaining 98.5% is bound to haemoglobin. Haemoglobin increases the oxygen-carrying capacity of blood approximately 70-fold.

Answer 3

Haemoglobin group is a tetrameter composed of 4 subunits Each subunit contains a polypeptide chain in association with a haem group. Haem group consists of a central charged iron atom held in a ring structure called porphyrin. 98% of adult haemoglobin is HBA1 which has 2 alpha chains and 2 beta chains HbA2 has 2 alpha chains and 2 delta chains HbF has 2 alpha and 2 gamma chains. HbF changes to HbA around 6 months of life

Answer 4

sickle cell anaemia is an inherited autosomal recessive blood disorder in which there is an abnormal β polypeptide chain due to a genetic mutation in the amino acid sequence where the amino acid valine is replaced by glutamic acid. in the heterozygous state this confers an advantage against malaria as the shortened lifespan of the erythrocyte prevents the blood-borne phase of the mosquito from completing its life cycle. in the homozygous state the abnormal haemoglobin is susceptible to forming solid, non-pliable sickle-like structures when exposed to low Pao2, causing the erythrocytes to obstruct the microcirculation, leading to painful crises and infarcts.

Answer 5

thalassaemia is an inherited autosomal recessive blood disorder in which the genetic defect results in a reduced rate of synthesis of one of the globin chains that make up haemoglobin. this can result in the formation of abnormal haemoglobin molecules, causing anaemia. thalassaemia can be α or β depending on which globin chain is being underproduced. thalassaemia is a quantitative problem where too few globin chains are synthesised, whereas sickle cell anaemia is a qualitative problem with the synthesis of an incorrectly functioning globin chain.

Answer 6

oxygen binds to the ferrous iron (Fe2+) in haemoglobin by forming a reversible bond. there is no oxidative reaction and so the iron atom always remains in the ferrous form. in the condition methaemoglobinaemia, the ferrous iron is oxidised into the ferric (Fe3+) form. each molecule of haemoglobin can bind four molecules of oxygen (i.e. one at each ferrous ion within each haem group). there are several factors that influence binding including local oxygen tension, local tissue environment (temperature, co2, hydrogen ions and 2,3 dPg) and the allosteric change and cooperative binding behaviour of oxygen to haemoglobin (see chapter 2, ‘oxygen–haemoglobin dissociation curve’, for further details).

Answer 7

even though dissolved oxygen represents a small fraction of total oxygen- carrying capacity of the blood, it still constitutes an important fraction. severe anaemia illustrates the point, e.g. for a Jehovah’s witness who has experienced a massive intra-operative haemorrhage and refuses blood transfusion. one therapeutic option would be the use of hyperbaric oxygen therapy; at three atmospheres and using 100% oxygen the dissolved fraction of oxygen would meet total body oxygen requirements. the dissolved fraction of oxygen is also responsible for triggering the hypoxic respiratory drive. this is of clinical significance in patients with coPd who are chronic co2 retainers, because giving them high-flow oxygen to increase their Pao2 may lead to loss of their hypoxic drive. in 2008, the british thoracic society published guidelines on the use of emergency oxygen in adults. the guidelines recommend that oxygen be administered to patients whose oxygen saturations fall below the target range (94–98% for most acutely ill patients and 88–92% for those at risk of type 2 respiratory failure with raised co2 levels in the blood).

Answer 8

Refers to the right shift in the oxygen dissociation curve which is in response to decreased pH, increased PaCO2 or increased temp. decreased oxygen affinity at low ph or high paco2 - facilitates release at tissues

Answer 9

this refers to the situation in the placenta where the bohr effect operates in both the maternal and fetal circulations. the increase in Pco2 in the maternal intervillous sinuses assists oxygen unloading. the decrease in Pco2 on the fetal side of the circulation assists oxygen loading. the bohr effect facilitates the reciprocal exchange of oxygen for carbon dioxide. the double bohr effect means that the oxygen dissociation curves for maternal Hba and fetal HbF move apart − i.e. right shift (maternal); left shift (fetal).

Answer 10

the Haldane effect describes the ability of hemoglobin to carry increased amounts of carbon dioxide (CO2) in the deoxygenated state as opposed to the oxygenated state. facilitates removal of co2 from the tissues

Answer 11

rectangular hyperbola also lies to the left of the OHDC due to myoglobin having a higher affinity for oxygen than haemoglobin